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Dark GDK / rate my work

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Gatorules
15
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Joined: 17th Dec 2008
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Posted: 22nd Jan 2009 05:44
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I am kinda new to c++ and dark basic but i tried to make this function and as far as i know it works. It is supposed to move a sprite at a set speed in a certain direction


void movesprite(int id, int direction, int speed, int image)
{
int obx=dbSpriteX(id);
int oby=dbSpriteY(id);

//sin(direction)*speed=x
float x=dbSin(direction)*speed;
//squareroot((speed*speed)-(x*x))=y
float y=dbSQRT( (speed*speed)-(x*x) );
if (direction>270 && direction<=360 || direction>=0 && direction<90)
{
dbSprite(id, obx+x, oby-y, image);
}
else
{
dbSprite(id, obx+x, oby+y, image);
}
}
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BatVink
Moderator
21
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Joined: 4th Apr 2003
Location: Gods own County, UK
Posted: 22nd Jan 2009 09:54
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I've moved this to the GDK board

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veltro
User Banned
Posted: 22nd Jan 2009 12:32 Edited at: 22nd Jan 2009 12:33
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If you use dbCos(direction) * speed to get the y offset you do not need to test the direction

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SunDawg
19
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Joined: 21st Dec 2004
Location: Massachusetts
Posted: 22nd Jan 2009 21:27
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I see you were trying to use the sin() function from the math header for C. The angle for that is supposed to be specified in radians (0 to 2*pi rather than 0 to 360), which would be why you were getting values you weren't expecting.


My site, for various stuff that I make.
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Gatorules
15
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Joined: 17th Dec 2008
Location:
Posted: 22nd Jan 2009 23:52
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Veltro, thank you for your comment. It seems to work, although i am not quite sure why, so i have changed my code to use it.

void movesprite(int id, int direction, int speed, int image)
{
int obx=dbSpriteX(id);
int oby=dbSpriteY(id);
float x=dbSin(direction)*speed;
float y=dbCos(direction)*speed;
dbSprite(id, obx+x, oby-y, image);
}
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